Printing and scanning apparatuses such as printers, scanners, copiers, and facsimile machines typically include automatic media feed systems. Automatic media feed systems introduce blank media, such as sheets of paper, into a printer or copier so that an image can be printed or reproduced on the media. Recently, individual printing and scanning apparatuses have been designed to perform multiple functions and handle various types of print media without interruption.
While modern printing and scanning apparatuses are often capable of scanning and printing multiple media types, it is common for the printing and scanning systems to require manual handling when media changes are required. The variety of media regularly used with such apparatuses includes labels, transparencies, and paper of various types and weights. Some specialized printers even accept objects such as optical discs (e.g. CDs and DVDs) for printing purposes.
FIG. 1 illustrates a typical a feed mechanism (100) used to supply media to a printing or scanning apparatus. As shown in FIG. 1, a typical feed mechanism (100) includes a pick-up roller (102) arranged adjacent to a fixed feed roller (106). The pick-up roller (102) facilitates the picking up of a print receiving media and introducing it to the printing or scanning apparatus. The pick-up roller (102) is generally biased toward the print receiving media by a spring (108) that applies a constant biasing force on the pick-up roller (102).
The biasing force supplied by the spring (108) is usually selected to effectively pick up the single most common media type used by the printing or scanning apparatus. While this typical feed mechanism (100) arrangement works fairly well for the intended media type, when media types other than the primary media type are used, too little force by the spring (108) can cause a misfeed due to the inability to slide the top sheet from the tray or stack. Alternatively, excessive force by the spring (108) causes a misfeed due to multiple sheets sliding from the media tray or stack. In either case, the efficiency of the printing process is significantly reduced.